The invention relates to a method for controlling heating processes in a coffee machine and an electronic control device.
Coffee machines in the prior art operate according to different principles. The most common models are the so-called pressureless coffee machines. In these water flows from a storage container into an electrically heatable pipe. Particularly as a result of the evolution of steam in this pipe, heated water is then pressed through a riser to an outlet via which the heated water then drips into a coffee filter. The filter coffee can then flow from this coffee filter at atmospheric pressure into a pot.
In contrast, in espresso machines an elevated pressure prevails in the area of the coffee grounds, for example 15 bar. This is achieved by supplying water from a water container or another water supply to an electric-motor-driven pump which then supplies the water at high pressure via an electrically heatable area to a coffee grounds receiving device. This coffee grounds receiving device generally comprises a filter for receiving the coffee. In order to generate the high pressure in the coffee area, during operation the coffee grounds receiving device is located in an area which is sealed towards the atmosphere, which can be designated as a pressure chamber or brewing chamber.
In another coffee machine which operates in a different principle, it is provided to first transfer the water for preparing the coffee from a water container into a heatable intermediate container. From this intermediate chamber the heated water is passed to an electric-motor-driven pump from which it is supplied at elevated pressure, for example 2 to 3 bar, to a coffee grounds receiving device. In this case, it is provided that unlike in the espresso machine the coffee is not introduced into the coffee grounds receiving device as coffee grounds but is inserted in a holder in the form of a coffee pad, that is, in compacted form surrounded by filter paper. The holder with a holder cover via which water is supplied can form a sealed pressure chamber. At the same time, the holder for the coffee pads is allocated a plurality of functions.
Firstly, the holders provides a sealing surface so that a pressure chamber can be formed. Moreover, the holder has an outlet opening from which the coffee can emerge. Furthermore, the coffee pad should be mounted in the holder in a manner such that flow through the coffee pad is not impeded. Such a coffee machine occupies an intermediate position between a conventional pressureless coffee machine and an espresso machine.
Coffee machines fitted with a continuous flow heater generally have a thermoblock. In many cases, such a thermoblock consists of cast aluminium with water-carrying channels being formed inside the block. Particularly controlled heating of the water can be achieved with a thermoblock, both with regard to the evolution of steam and the constant nature of the coffee temperature. However, thermoblocks are expensive to manufacture and they require a relatively large mass to store the heat.
Continuous-flow heaters without a thermoblock are cost-effective but have some disadvantages when operated with coffee pads, should the hot coffee be required to be available immediately in a short time at a specific temperature and the time sequence for a cup is very short.
The disadvantages include uncontrolled evolution of steam with corresponding excess pressure, and a high dependence of the coffee outlet temperature on factors such as water temperature in the tank, ambient temperature, mains voltage fluctuations and tolerances of the heater.
It is the object of the invention to provide a method and an electronic control device on the basis of which a coffee machine can also be operated satisfactorily without a thermoblock.